It seems like during setup, eero doesn't consider the signal from wired connection. It would refuse to add a new eero if has poor wireless connection, even if it's hardwired to the first gateway eero? Is this the expected behaviour? Can this be changed in future updates?

I've worked around the problem by setting up the second eero while it's close to the first one, and move it to where I really want it after it's added. The wired backhaul works, but it'd be much better if the setup was easier.